This invention relates to an ink jet recording apparatus with an improved ink sensor, particularly to an ink sensor which is used for detecting disorder in recording.
In an ink jet recording apparatus, ink under pressure is vibrated with a constant frequency at a nozzle of the apparatus. Therefore, the ink emitted from the nozzle becomes droplets of a constant size with a regular interval. The ink droplets are charged by a charging plate in accordance with electric voltage applied thereto.
In this kind of ink jet recording apparatus a problem may occur often such that the phase between emission of ink droplets out of the nozzle and charging thereof does not accord, which may result in disorder in recording. Accordingly the phase should be corrected.
In order to detect disorder in record, a microphone, which is disposed in a flying path of the ink droplets to be detected and converts impinging energy of the ink particles into an electric signal, has been used. The microphone, however, has the following defects or disadvantages:
1. Since the ink droplets impinge directly with a diaphragm of the microphone, it needs to be completely water-proof, which results in difficulty of manufacture thereof and raising the cost thereof.
2. Since the deflection amount of the ink droplets charged is small, it is necessary to construct the microphone into a small size, which is difficult in manufacture thereof.
3. A vibrating face of a conventional microphone varies in sensibility according to the position at which the ink droplets impinge therewith, and it is necessary to adjust the microphone such that ink droplets impinge with the highest sensibility position of the microphone. Therefore the adjustment becomes difficult.
Further known is an ink sensor comprising an induction rod of which one end is disposed to face a flying path of ink droplets to be detected and a pair of shielding plates between which the end of the induction rod is disposed. The shielding plates each are provided with a hole through which the ink droplets pass. In this sensor, it is difficult to adjust the position of the sensor relating to the ink jet recording apparatus without contacting the flying ink droplets with the shielding plates.